Fast proton transport in zinc phosphorous glass composites

► Proton conduction in various TiO2-ZnO-P2O5 systems at intermediate temperatures. ► P2O5-excess non-stoichiometric Ti1−xZnxP2O7 shows high conductivity (>10−3 S cm−1). ► ZnO-P2O5 glass formed on the surface of TiP2O7 also shows the high conductivity. ► Fast proton transport at the interface between the ZnO-P2O5 glass and TiP2O7. ► A model with fast interfacial transport explains the conductivity characteristics.